In recent decades, many different hypotheses have been proposed about what the neurobiological bases for panic disorder may be. One that best explains the symptoms of this disorder suggests that panic originates from an abnormally-sensitive fear circuit, in which the critical areas would be the amygdalo-hippocampal region, its projections and the prefrontal medial cortex. Via fMRI, we want to study the physiopathological mechanisms involved in panic disorder (PD), especially focusing on what the implicit processing of threatening stimuli in these patients is. Concretely, we propose studying the response to masked threatening stimuli using the same subsequent masking procedure that has been proven to interrupt the processing of emotional faces in patients affected by PD. A functional MRI protocol will be applied to patients with PD and a comparable group of volunteers without. After the patients have had treatment with cognitive-behavioural psychotherapy (CBT), we will compare the results we obtained previously with a new acquisition of functional MRI.